The Effect of Sm Addition on the Microstructure and Superconducting Properties of YBCO Bulk Superconductors

Abstract

The effect of Sm addition on the microstructure and superconducting properties of Y-Ba-Cu-O (YBCO) bulk superconductors has been studied. Nominal composition: 1 mol YBa2Cu3O 7−δ + 0.25 mol Y2O3+ 1 wt% CeO2 was enriched with different amounts of SmBa2Cu3Oy powder with the aim to increase critical current density, Jc, especially in higher magnetic fields by introducing additional pinning centers. Single grain YBCO bulk superconductors with SmBa2Cu3Oy (Y123-Sm) addition were prepared by the optimized top seeded melt growth process. Microstructure analysis, performed by polarized light microscope, revealed that SmBa2Cu3Oy addition leads to a higher amount of slightly coarser Y2BaCuO5 particles, which is related to lower critical current densities (Jc ≈ 6 × 10 4 A/cm 2 ) of the YBCO samples with SmBa2Cu3Oy addition in low magnetic fields. On the other hand, an enhancement of critical current density, Jc, in higher magnetic fields was observed for Y123-Sm samples. Moreover, a maximum trapped magnetic field, Btmax, of 564 mT at 77 K in Y123-Sm, x = 0.0025 sample (Ø17.2 mm) was 43% higher than that for YBCO sample without any addition.

Relationship between local microstructure and superconducting properties of commercial YBa2Cu3O7−δ bulk

“…In the case of 1c and 2c samples J c substantially increased for the sample 1c at higher magnetic fields (figure 8(a)) due to the presence of inhomogeneities in the crystal structure which improve the flux pinning process. We suppose that these inhomogeneities in the sample 1c were created by possible neodymium contamination of Y123 from the seed during solidification process [31,32]. However, chemical elemental mapping of the bulk using SEM in the vicinity of the seed did not detect neodymium that most probably could be caused by its concentration below energy dispersive x-ray spectroscopy detection limit which is 0.1 wt%.…”